The present invention relates to a new and improved construction of filter assembly for removing or recovering respectively, fine or particulate, especially fibrous solid materials from a gas or air stream, respectively.
For cleaning large quantities of gas or air or for the return of waste therefrom, there are required filters, for instance in the textile technology, the asbestos or reinforced fibre art and for other processing methods where there occur health-hazardous suspendable solid particles which may cause, for instance, byssinosis.
Devices serving this purpose have been known to the art for a long time, for instance from British Pat. No. 16,392, U.S. Pat. No. 2,722,997 and German Pat. No. 2,751,789. Common to all these prior art devices is a separator provided with a filter drum which is open at one side and equipped with an approximately cylindrical stationary jacket or shell. This jacket or shell is formed of a material for instance a textile material or fibre fleece, which is gas-pervious but retains the fine or particulate solid particles entrained in the gas stream. The stationary filter drum is impinged through its free end by the gas stream which is to be filtered and this gas stream is conveyed by a forwardly arranged pressure blower or a subsequently arranged suction blower. The solid materials separated at the inner surface or side of the filter jacekt or shell have to be removed. From the initially mentioned British Pat. No. 16,362, filed in 1911, there has been known for quite some time the proposal of employing, for this purpose, suction nozzles which are intended to suck-off the solid materials separated at the inner surface of the filter jacket. Accordingly, the apparatus disclosed in this British Pat. No. 16,392 is provided with a coaxially arranged rotating hollow shaft. Connected to this hollow shaft in a manner so as to be non-movable in radial and axial direction are the suction nozzles. By means of a separate suction blower the solid matrials are sucked-off through the suction nozzles and the hollow shaft. In order to suck-off te entire inner surface of the filter jacket or shell there are employed a number of substantially slot-shaped, adjacently arranged suction nozzles, each of which extends in axial direction over a partial area of the inner surface, or there is employed a single suction nozzle whose suction slot extends axially over the entire axial length of the inner surface of the filter jacket. In both instances the suction nozzles pass through linear, substantially circular-shaped paths. However, a sufficient uniform suction effect upon the inner surface of the filter jacket heretofore has not been achievable with a practicable expenditure in equipment especially if the filter drum is stationary.
While there are known to the art, for instance from Swiss Pat. No. 591,054, oscillating suction nozzles which are displaceable in axial direction and arranged internally of the filter drum, such suction nozzles only can be used with rotating filter drums which are provided in axial direction with stationary suction nozzles, and this arrangement requires a separate drive for the oscillating motion in axial direction.
In order to avoid the disadvantages of internally sucking-off a stationary filter drum according to British Pat. No. 16,392, there has become known to the art from the aforementioned U.S. Pat. No. 2,722,997 and the German Pat. No. 2,751,789 the proposal of replacing the internally arranged suction nozzles by oscillating blast rings which are arranged externally of the filter drum. For this purpose, there is employed a substantially annular or ring-shaped tube which is provided with blast openings and which is displaced with an oscillating motion at the outside of the filter jacket in its axial direction by means of a motor. This annular or ring-shaped tube blows-off with pressurized air, against the main stream, the solid materials deposited at the inside of the filter jacket or shell. The thus blown-off solid materials are sucked-off through separate suction devices provided in the internal space of the filter drum, or they are sucked-off close to the floor of the drum, depending upon whether the axis of the filter drum is arranged vertically, according to the U.S. Pat. No. 2,722,997, or horizontally, according to the German Pat. No. 2,751,789.
However, as opposed to internally sucking-off the solid materials, blowing-off the same from the outside is associated with functional, especially aerodynamic and energy-related as well as constructional disadvantages.